Control System for a High-Speed Elevator Using Digital and Logic Elements
Abstract Generated abstract
This paper presents an experimental automatic control and signaling system for a high-speed elevator using contactless digital and logic elements in place of bulky relay-contactor equipment. It describes a digital tracking system composed of command and call storage devices, a computing unit, and a reversible binary car-position counter, with logic circuits synthesized to select travel direction, process calls and commands, and issue stop commands. The proposed architecture stores elevator position and service requests in binary form, compares them through AND, OR, and NOT logic, and supports precise stopping and direction-dependent call handling, illustrating how computing-device elements can simplify and improve elevator automation.
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CONTROL SYSTEM FOR A HIGH-SPEED ELEVATOR BASED ON DIGITAL AND LOGIC ELEMENTS
V. Z. YAMPOLSKII, V. B. TEREKHIN, A. I. ZAITSEV
(Presented by the scientific seminar of the Electromechanical Faculty)
Automatic control of high-speed and very-high-speed elevators provides for the following main functions: selection of the direction of travel, processing of calls and commands, deceleration before an exact stop, various kinds of signaling, etc.
The high level of automation of high-speed elevators has led to a very complex electrical circuit. This system was implemented by means of relay-contactor equipment. The abundance of relay-contactor equipment in a system with a large number of contacts complicates operation and leads to an increased probability of failures in the system.
In addition, the system of automatic control and signaling of an elevator installation, in order to ensure the automatic execution of a number of technological tasks, must be capable of solving logical problems that arise during elevator operation. Solving a large number of logical problems by means of relay-contactor equipment does not appear possible, because of the excessive bulkiness of the solutions obtained.
The use of new means of automation—elements of contactless automation and elements of computing devices—for the automation of high-speed elevators provides a higher-quality solution to this problem.
The system presented here was developed on the basis of the design assignment of the Central Design Bureau “Electric Drive” (VNIIEM) for the creation of an experimental system, in which all technological functions of the individual units of the automation and signaling system are taken into account, and whose solution must be provided by means of contactless automation with the use of computing elements.
Control System
The main unit ensuring the automatic operation of the elevator is the digital tracking system—DTS.
The DTS consists of an information input device, a computing device, and a car-position counter.
The block diagram of the automation system is shown in Fig. 1. The input device (UV) contains two storage devices: for commands (ZUP) and for calls (ZUV), in which commands arriving from the car via the telechannel, and calls arriving from the floor landings, are recorded and stored until they are executed.
The car-position counter (SPK) is intended for storing information on the current position of the car in digital form. When the car is moving upward, the counter operates in addition mode; when moving downward, in subtraction mode.
When a floor sensor (DE) is passed, the number in the counter is increased or decreased by one, depending on the direction of travel. Switching the counter to addition or subtraction is performed automatically.
The computing device (VU) compares the current position of the car with the position specified by a call or command.
Fig. 1.
Information is entered into the VU in binary code. The computing device compares the above-mentioned quantities, and if the digit (of the command or call) from the input device is greater than the digit (of the current car position) from the position counter, then the command “Up” is generated; if it is smaller, “Down”; and, finally, if they are equal, “Stop.” The “Stop” command causes the drive speed to be reduced and brings into operation the precision stopping system (STO), which brings the car to the specified floor.
The VU consists of two identical units: the command computing unit and the call computing unit. The “Up” and “Down” commands of the call computing unit are executed only when there are no passengers in the car, while the “Stop” command is generated only for calls in the same direction of travel.
A description of the individual units of the system is given below.
Command Storage Device
The device is implemented on static triggers, the number of which is equal to the number of elevator stops.
The schematic diagram of the storage device is shown in Fig. 2.
Fig. 2.
Commands arriving from the car are fed to the input of the triggers of the cells and switch them from state “0” (unexcited) to state—
state “1” (energized). The output of each flip-flop is fed to two coincidence circuits, which are switched by the control flip-flop. When moving “Up,” the control flip-flop gives permission to all the left-hand coincidence circuits and inhibits all the right-hand circuits. The outputs of each cell, through the collecting “OR” circuit, go to the circuit for converting the floor number into binary code and then to the input of the computing device.
The CSU coincidence circuits are interlocked in such a way that, at every moment of time, the nearest command in the direction of elevator travel is applied to the input of the computing device.
Call storage device
The principle of its construction is analogous to that of the CSU. The CSU cell consists of three static flip-flops: a flip-flop for storing up calls, a flip-flop for storing down calls, and an intermediate flip-flop. The intermediate storage device is intended for the temporary storage of calls in the case when the inhibit circuit does not permit the call to be recorded in the cell of the up or down flip-flop.
The write switching circuit operates in accordance with Table 1.
Table 1
| Z | V | N | \(P_{\mathrm{v}}\) | \(P_{\mathrm{n}}\) | \(P_{\mathrm{p}}\) |
|---|---|---|---|---|---|
| 1 | 1 | 0 | 0 | 1 | 1 |
| 1 | 0 | 1 | 1 | 0 | 1 |
| 0 | 1 | 0 | 1 | 1 | 0 |
| 0 | 0 | 1 | 1 | 1 | 0 |
The derivation of the structural formula for \(P_{\mathrm{v}}\), \(P_{\mathrm{n}}\) is carried out from the false conditions (by zeros), and for \(P_{\mathrm{p}}\) from the true conditions (by ones) [2]. Consequently,
\[ \overline{P}_{\mathrm{v}} = Z \cdot V \cdot \overline{N}, \]
\[ \overline{P}_{\mathrm{n}} = Z \cdot \overline{V} \cdot N, \]
\[ P_{\mathrm{p}} = Z \cdot V \cdot \overline{N} + Z \cdot \overline{V} \cdot N . \]
The circuit implementing these structural formulas is shown in Fig. 3.
In the same figure, the complete circuit of a CSD cell is presented.
Fig. 3.
Computing device
The computing device is intended for the automatic determination of the direction of motion of the elevator car and for generating the “Stop” command according to commands and calls.
The computing device was developed using code-position logic elements AND, OR, NOT.
The synthesis of the computing device was carried out by the matrix method according to Table 2.
Table 2
| $b_1b_2b_3 \backslash a_1a_2a_3$ | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|---|---|---|---|---|---|---|---|
| 1 | C | D | D | D | D | D | D | D |
| 2 | U | C | D | D | D | D | D | D |
| 3 | U | U | C | D | D | D | D | D |
| 4 | U | U | U | C | D | D | D | D |
| 5 | U | U | U | U | C | D | D | D |
| 6 | U | U | U | U | U | C | D | D |
| 7 | U | U | U | U | U | U | C | D |
| 8 | U | U | U | U | U | U | U | C |
In Table 2 the following notation is used:
C — “Stop,” U — “Up,” D — “Down”;
$a_1, a_2, a_3$ — states of the digits of the reversible counter of the current position,
$b_1, b_2, b_3$ — coordinates of the call or command in binary code.
The table was compiled on the basis of the operating logic of the computing device for all possible states of the input variables $a_1, a_2, a_3$ and $b_1, b_2, b_3$.
For example, for the command “Stop” the structural formula for the operating conditions of the logic circuit, the composition of its principal logic elements, and the order of their interconnection are represented by the following notation in symbolic form:
\[ \bar a_1 \bar a_2 \bar a_3 \bar b_1 \bar b_2 \bar b_3 + a_1 \bar a_2 \bar a_3 b_1 \bar b_2 \bar b_3 + \bar a_1 a_2 \bar a_3 \bar b_1 b_2 \bar b_3 + a_1 a_2 \bar a_3 b_1 b_2 \bar b_3 + \bar a_1 \bar a_2 a_3 \bar b_1 \bar b_2 b_3 + \]
\[ + a_1 \bar a_2 a_3 b_1 \bar b_2 b_3 + \bar a_1 a_2 a_3 \bar b_1 b_2 b_3 + a_1 a_2 a_3 b_1 b_2 b_3 . \]
This structural formula is easily simplified by using the basic laws of the algebra of logic [1].
\[ \bar a_3 \bar b_3 \left[ \bar a_2 \bar b_2(\bar a_1 \bar b_1 + a_1 b_1) + a_2 b_2(\bar a_1 \bar b_1 + a_1 b_1) \right] + a_3 b_3 \left[ \bar a_2 \bar b_2(\bar a_1 \bar b_1 + a_1 b_1) + \right. \]
\[ \left. + a_2 b_2(\bar a_1 \bar b_1 + a_1 b_1) \right] = (\bar a_1 \bar b_1 + a_1 b_1) (\bar a_2 \bar b_2 + a_2 b_2) (\bar a_3 \bar b_3 + a_3 b_3). \]
This logical formula corresponds to the functional diagram shown in Fig. 4.
Fig. 4.
Car-position counter
To obtain information about the position of the car in the shaft, a reversible binary counter is used, the circuit of which is shown in Fig. 5.
The counter operates as follows. When the elevator moves, pulses from the car-position sensors installed in the shaft arrive at the counter input, two sensors for each floor.
Fig. 5.
These pulses are added to the number stored in the counter, or subtracted from it, depending on the state of the sign trigger T. S.
The sign trigger is controlled by commands generated by the computing device.
When moving “Up,” the addition bus has a high potential level, opens the addition valves \(B_1, B_3\), which determine the operation of the counter for addition.
During “Down” motion, the subtraction gates \(B_2\), \(B_4\) are open; these switch the operation of the counter from addition to subtraction.
Thus, at every moment of time the counter stores a number that constitutes information on the current position of the elevator car in the shaft. The counter is made using static flip-flops on planar semiconductor transistors. Fig. 6 shows the elementary circuit of a flip-flop.
Fig. 6.
REFERENCES
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D. A. Pospelov. Arithmetic and Logical Foundations of Discrete-Action Computing Machines. MPEI Publishing House, 1951.
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E. A. Drozdov, V. I. Prokhorov, A. P. Pyatibratov. Fundamentals of Computing Technology. Military Publishing House, 1961.
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M. M. Sokolov. Electrical Equipment of General-Industrial Mechanisms. Gosenergoizdat, 1959.
Received by the editors
in May 1962.